I have precipitates of ferric hydroxide and I know if I add hydrochloric acid in it I will get the precipitates of ferric chloride.. how can then I determine the molarity of ferric chloride formed?

i have precipitates of ferric hydroxide and i know if i add hydrochloric acid in it i will get the precipitates of ferric chloride..how can then i determine the molarity of ferric chloride formed?

Not easily. Ferric chloride is relatively soluble in water. At 25degC, it would take a 50% solution to precipitate ferric chloride. If titrating a ferric hydroxide slurry to find out the ferric ion molarity is your goal, divide one third of the number of liters of 1M HCl is takes to dissolve your ferric hydroxide by the total liters of solution at the endpoint. This will probably only be a rough estimate because of the possible solubility of ferric hydroxide or other ions present.